Cpu Usage

[loaded]

Hi all
When the sample code is running;

Code: Pascal  [Select][+][-]

1. var
2.   test:integer=0;
3. begin
4.  repeat
5.  inc(test,1);
6.  until test>High(integer);
7.  

In the Process Explorer program when examining processor, So why not reach a hundred ?

[Thaddy]

You have a quad core, so it's just 25% One core fully occupied at 100%.

[loaded]

Thanks Thaddy
So, how do we get it to 100%
or
What should we do in order to use 4 cores simultaneously.

[mig-31]

TThread

[loaded]

Thanks mig-31
See coincidence: Well you respond, I was looking into https://tr.wikipedia.org/wiki/mig-29 page 

TThread, Can you give an example regarding the issue?

[Thaddy]

Very quick, very dirty but it will eat 100% cpu time for a little

Code: Pascal  [Select][+][-]

1. program untitled;
2. {$ifdef fpc}{$mode delphi}{$endif}
3. uses
4.   {$ifdef unix}cthreads,{$endif}classes;
5. type  
6.   TMyThread= class(TThread)
7.   procedure Execute;override;
8.   end;
9.   procedure TMyThread.Execute;
10.   var
11.     test:integer=0;
12.     begin
13.       repeat
14.       inc(test);
15.     until test>=High(integer);
16.   end;
17. var
18.  T:Array[0..3] of TMyThread;
19.  s:string;
20. begin
21.   S:='';
22.  var
23.  T:Array[0..3] of TMyThread;
24.  s:string;
25. begin
26.   S:='';
27.   T[0] := TMyThread.Create(false);T[0].FreeOnTerminate := true;
28.   T[1] := TMyThread.Create(false);T[1].FreeOnTerminate := true;
29.   T[2] := TMyThread.Create(false);T[2].FreeOnTerminate := true;
30.   T[3] := TMyThread.Create(false);T[3].FreeOnTerminate := true;
31.  
32.   repeat
33.     readln(s);
34.   until length(s) > 0;
35.  
36.  end.

[loaded]

Very thanks Thaddy
Codes worked. CPU usage reached 100.
But the problem has occurred.
Threads are running slow:
The main thread running codes in 3.83 ms, 5:21 ms took the thread particles.
Is there any way we can speed up the thread?

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, StdCtrls;
9.  
10.  
11. type
12.   TMyThread= class(TThread)
13.   procedure Execute;override;
14.   public
15.     timed:cardinal;
16.     starts:integer;
17.     stopts:integer;
18.  
19.   end;
20.  
21. type
22.  
23.   { TForm1 }
24.  
25.   TForm1 = class(TForm)
26.     Button1: TButton;
27.     Button2: TButton;
28.     Button3: TButton;
29.     procedure Button1Click(Sender: TObject);
30.     procedure Button2Click(Sender: TObject);
31.     procedure Button3Click(Sender: TObject);
32.   private
33.     { private declarations }
34.   public
35.     { public declarations }
36.   end;
37.  
38. var
39.   Form1: TForm1;
40. var
41.  T:Array[0..3] of TMyThread;
42. implementation
43.  
44. {$R *.lfm}
45.  
46. { TForm1 }
47.  
48.  
49. procedure TMyThread.Execute;
50. var
51.   test:integer=0;
52.   crono:cardinal;
53.   begin
54.     crono:=GetTickCount;
55.     for test:=starts to stopts do ;
56.     timed:=GetTickCount-crono;
57. end;
58.  
59. procedure TForm1.Button1Click(Sender: TObject);
60. begin
61.   T[0] := TMyThread.Create(false);
62.   T[0].starts:=0;
63.   T[0].stopts:=536870911;
64.   T[0].FreeOnTerminate := true;
65.  
66.  
67.   T[1] := TMyThread.Create(false);
68.   T[1].starts:=536870912;
69.   T[1].stopts:=1073741822;
70.   T[1].FreeOnTerminate := true;
71.  
72.  
73.   T[2] := TMyThread.Create(false);
74.   T[2].starts:=1073741823;
75.   T[2].stopts:=1610612733;
76.   T[2].FreeOnTerminate := true;
77.  
78.  
79.   T[3] := TMyThread.Create(false);
80.   T[3].starts:=1610612734;
81.   T[3].stopts:=2147483647;
82.   T[3].FreeOnTerminate := true;
83.  
84. end;
85.  
86. procedure TForm1.Button2Click(Sender: TObject);
87. var
88.   test:integer=0;
89.   crono:cardinal;
90.   begin
91.     crono:=GetTickCount;
92.     repeat
93.     inc(test);
94.     until test>=High(integer);
95.     showmessage('Total run time of Main thread : ' + floattostr((GetTickCount-crono)/1000));
96. end;
97.  
98. procedure TForm1.Button3Click(Sender: TObject);
99. begin
100.   showmessage('Total run time of all threads : ' + floattostr(( T[0].timed+T[1].timed+T[2].timed+T[3].timed)/1000));
101.  
102. end;
103.  
104. end.
105.  

[Fungus]

Increase thread priority: http://www.freepascal.org/docs-html/rtl/classes/tthread.priority.html

[marcov]

Note that depending on the CPU it can be that this defeats turboboost.

IOW if only one core is occupied, the CPU increases its frequency, but if all four are active, it won't. Specially on quadcore laptop this can be significant frequency difference (e.g. mine has a 2.2GHz base frequency and a 3.2GHz turboboost)

[Thaddy]

Also code alignment is sometimes an issue on intels.
Try {$codealign=16}

Also note that threading has a slight speed disadvantage per thread, but still should run close to 4 times faster in total.
This is due to the caches and maybe a shared cache depending on processor model.

[Thaddy]

Increase thread priority: http://www.freepascal.org/docs-html/rtl/classes/tthread.priority.html

That is nonsense really not necessary. The 4 threads will eat all cores. They are closed loops.

[Thaddy]

5:21 ms took the thread particles.

I put in a delay. The delay is the cause, not the threads.
Also note the example was really quick and really dirty.
don't use it in the real world, it was just to demonstrate how to get the cpu's fully loaded.
There is a lot to optimize besides caching, pipelining and code aligning.

[loaded]

Very Thanks Fungus,marcov,Thaddy

Hey Fungus,

Increase thread priority: http://www.freepascal.org/docs-html/rtl/classes/tthread.priority.html

The suggestion, I added the following code.

Code: Pascal  [Select][+][-]

1. ...
2. T[0].Priority:=tpTimeCritical;
3. ...
4.  

threads accelerated, but was undecided,
sometimes 0.9 ms
sometimes 1.82 ms
sometimes 4.9 ms
This can cause ?

Thaddy , Can you give a simple example,could you please ?

[rvk]

You start your thread directly when create it: TMyThread.Create(false);
(the false is for the CreateSuspended parameter)

You need to set the priority before executing the thread. Also... the assignment of starts and stops could be too late as the thread might have already started with the execution. So you could need to override Create() with your parameters and set them in create() of create the thread with CreateSuspended = true. Like so:

Code: Pascal  [Select][+][-]

1.   T[0] := TMyThread.Create(true);
2.   T[0].starts := 0;
3.   T[0].stopts := 536870911;
4.   T[0].FreeOnTerminate := true;
5.   T[0].Priority := tpTimeCritical;
6.   T[0].Resume;

O, and B.T.W. your program only runs for about 2 or 3 seconds for me. The loops are too short to really see the CPU go to 100%.
If you change it to "repeat until false;" then it will run forever (or until you kill the program).

4 thread got me to 60%
6 thread got me to 88%
On a machine with 4 cores and 8 threads according to CPU-Z.

Edit: Woops... well. if you really want the 100% you need to create 8 threads (as stated by cpu-z). It locked my system up completely (needed to do a hard reboot). Don't forget to make the loop longer but not indefinite because then you'll have to restart you machine too

What does having 4 cores and 8 threads?

[Fungus]

Very Thanks Fungus,marcov,Thaddy

Code: Pascal  [Select][+][-]

1. ...
2. T[0].Priority:=tpTimeCritical;
3. ...
4.  

threads accelerated, but was undecided,
sometimes 0.9 ms
sometimes 1.82 ms
sometimes 4.9 ms
This can cause ?

Nice to see a speed gain although someone considered the suggestion nonsense. You will never get "clean" CPU when your application is run in an operating system. Other (background) processes will require CPU once in a while and the system will grant this even if your process runs at highest priority. To get less variance you must increase the loop length - you could put in a time check that allows the loops to run for 10 (or more) seconds to decrease variance.

Code: Pascal  [Select][+][-]

1. Var Tick: Int64;
2. Begin
3.   Tick:= GetTickCount64;
4.   Repeat
5.     //Loop code here
6.   Until GetTickCount64 - Tick >= 10000; //10 seconds (10 times 1000 milliseconds)
7. End;
8.